Fundamental Implications of Fields, Strings and Gravity

场、弦和引力的基本含义

基本信息

批准号：
ST/L000490/1
负责人：
Konstadinos Sfetsos
金额：
$ 34.55万
依托单位：
University of Surrey
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2014
资助国家：
英国
起止时间：
2014 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=ST%2FL000490%2F1
关键词：
Fundamental Implications Fields Strings Gravity

项目摘要

Newtonian physics describes our universe well, provided the objects of interest are not too small, do not move too fast, or are not too dense. At a small length scales, Newtonian physics is replaced by quantum physics. In addition, if interactions involve speeds close to that of light, then quantum physics is replaced by quantum field theory (QFT). This theory is a milestone of scientific discovery and underpins all experimentally verified particles and interactions. The standard approach to QFT relies on perturbation theory, which assumes that all interactions are weak. There are many situations where that is not the case, and the resulting theory is said to be strongly coupled. In the theory underlying the standard model of particle physics the interactions are generally not weak. This prevents us from explaining phenomena such as the confinement of quarks to form the protons and neutrons that make up matter. This is a conceptual problem, and a major limitation for phenomenological applications.What about if we are dealing with extremely dense objects? For example, if all of the matter inside the Earth were compressed to fill a sphere with a radius of a few millimetres, then the above theories would break down. In this case, one would need to incorporate Einstein's theory of general relativity with quantum field theory. However, there is no completely consistent way to do this, leaving a gaping hole in our understanding of the universe. The only theory that successfully combines QFT with general relativity is string theory. Self-consistency of the theory demands stringent mathematical conditions be imposed. For example, there must exist six extra spatial dimensions in addition to the three spatial dimensions we are accustomed to. To resolve this, one must ``compactify'', i.e. posit that the extra dimensions span curled geometries, not visible to present day experiment. A rough analogy is with a hose: from a distance it looks one-dimensional, but on closer inspection there is an additional circular direction. Describing the physics of the observable universe becomes a problem closely tied to the geometry of certain spaces.Remarkably, string theory has led to new ideas concerning the description of strongly coupled QFTs. One such tool, known as holography, represents the idea that our space-time encodes information of a higher dimensional one, much like a hologram is a two-dimensional representation of a three-dimensional picture. It turns out that the strongly coupled QFT in four-dimensions relates to a weakly coupled five-dimensional gravity theory in which we may apply perturbative techniques to perform computations. Over the past decade, this idea has led to many new and exciting developments in theoretical physics. It has also been used to understand experimental results obtained under extreme pressure and temperature conditions (quark gluon plasma). The aims of this project are two-fold: to use these new tools from string theory to understand the strongly coupled regime of QFT; and to use string theory to model the four-dimensional space time observed today. For example, many of the ideas and concepts within string theory have drastically changed the way we think about strongly coupled QFTs. There are also new examples of strongly coupled QFTs, in which calculations have become tractable. Although not realistic models, they share with the real world many common qualitative features, which are otherwise hard to understand. By studying these new examples we hope to shed light on how obscure mechanisms such as confinement work in theories of experimental interest. By utilising these developments in quantum field theory we hope to undercover the exact conditions required to reproduce the string compactification that describes modern particle physics.

牛顿物理学很好地描述了我们的宇宙，只要感兴趣的对象不太小，不要过速或不太密度。在较小的尺度上，牛顿物理学被量子物理代替。另外，如果相互作用涉及接近光的速度，则量子物理学将被量子场理论（QFT）取代。该理论是科学发现的里程碑，并且是所有实验验证的粒子和相互作用的基础。 QFT的标准方法依赖于扰动理论，该理论假定所有相互作用都是薄弱的。在许多情况下，情况并非如此，因此所产生的理论被强烈耦合。在粒子物理标准模型的基础理论中，相互作用通常并不弱。这样可以阻止我们解释现象，例如夸克夸克形成构成重要的质子和中子。这是一个概念上的问题，也是现象学应用的主要限制。如果我们要处理极其密集的对象，这是什么？例如，如果将地球内部的所有物质压缩到一个半径上的几毫米，则上述理论将分解。在这种情况下，人们需要将爱因斯坦的一般相对性理论与量子场理论结合在一起。但是，没有完全一致的方法可以做到这一点，在我们对宇宙的理解中留下了一个巨大的漏洞。成功将QFT与一般相对性结合的唯一理论是字符串理论。该理论的自矛盾需要严格的数学条件。例如，除了我们习惯的三个空间维度外，还必须存在六个额外的空间维度。为了解决这个问题，必须``压实''，即认为，额外的尺寸涵盖了卷曲的几何形状，在当今的实验中看不到。一个粗糙的类比是软管：从远处看，它看起来一维，但是在仔细检查时，还有一个额外的圆形方向。描述可观察到的宇宙的物理学成为与某些空间几何形状紧密相关的一个问题。值得注意的是，弦理论导致了有关强烈耦合QFT的描述的新思想。一种这样的工具称为全息图，代表了我们的时空编码更高维度的信息，就像全息图一样，是三维图片的二维表示。事实证明，四维中强耦合的QFT与弱耦合的五维重力理论有关，我们可以将扰动技术应用于执行计算。在过去的十年中，这个想法导致了理论物理学的许多新的令人兴奋的发展。它也已被用来理解在极端压力和温度条件下获得的实验结果（夸克·格鲁恩等离子体）。该项目的目的是两个方面：使用字符串理论中的这些新工具来了解QFT的强烈耦合制度；并使用弦理论来建模今天观察到的四维空间时间。例如，字符串理论中的许多思想和概念都大大改变了我们对QFT的强烈耦合的方式。也有强烈耦合QFT的新示例，其中计算变得可拖动。尽管不是现实的模型，但它们与现实世界分享了许多常见的定性特征，否则这些特征很难理解。通过研究这些新示例，我们希望阐明如何在实验兴趣理论中限制诸如限制工作等晦涩的机制。通过在量子场理论中利用这些发展，我们希望秘密地介绍描述现代粒子物理学的弦乐紧凑型所需的确切条件。